Re: [PATCH 3/3] acpi, memory-hotplug: Support getting hotplug info from SRAT.

[Tang Chen <tangchen@cn.fujitsu.com>]

On 02/05/2013 07:26 AM, Andrew Morton wrote:
> On Fri, 25 Jan 2013 17:42:09 +0800
> Tang Chen<tangchen@cn.fujitsu.com>  wrote:
>
>> We now provide an option for users who don't want to specify physical
>> memory address in kernel commandline.
>>
>>          /*
>>           * For movablemem_map=acpi:
>>           *
>>           * SRAT:                |_____| |_____| |_________| |_________| ......
>>           * node id:                0       1         1           2
>>           * hotpluggable:           n       y         y           n
>>           * movablemem_map:              |_____| |_________|
>>           *
>>           * Using movablemem_map, we can prevent memblock from allocating memory
>>           * on ZONE_MOVABLE at boot time.
>>           */
>>
>> So user just specify movablemem_map=acpi, and the kernel will use hotpluggable
>> info in SRAT to determine which memory ranges should be set as ZONE_MOVABLE.
>>
>> ...
>>
>> +	if (!strncmp(p, "acpi", max(4, strlen(p))))
>> +		movablemem_map.acpi = true;
>
> Generates a warning:
>
> mm/page_alloc.c: In function 'cmdline_parse_movablemem_map':
> mm/page_alloc.c:5312: warning: comparison of distinct pointer types lacks a cast
>
> due to max(int, size_t).
>
> This is easily fixed, but the code looks rather pointless.  If the
> incoming string is supposed to be exactly "acpi" then use strcmp().  If
> the incoming string must start with "acpi" then use strncmp(p, "acpi", 4).
>
> IOW, the max is unneeded?

Hi Andrew,

I think I made another mistake here. I meant to use min(4, strlen(p)) in 
case p is
something like 'aaa' whose length is less then 4. But I mistook it with 
max().

But after I dig into strcmp() in the kernel, I think it is OK to use 
strcmp().
min() or max() is not needed.

Thanks. :)

>
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